1. Field of the Invention
The present invention relates to a high voltage generator for generating a higher voltage than a voltage of a power source by using a principle of pumping in a semiconductor memory apparatus and, more particularly, to a high voltage generator capable of selecting one of two types of pumps in case of two different external voltages, thereby obtaining a high pumping efficiency and improving a pumping stability without a latch-up phenomenon.
2. Discussion of Related Art
Generally, a high voltage (hereinafter, referred to as a Vpp) generator is an apparatus for applying a constant high voltage to a circuit within a chip requiring a higher voltage than an external voltage Vcc in a semiconductor device. Such the Vpp generator comprises a level detector for detecting a Vpp potential level and outputting the corresponding signal, a ring oscillator for generating pulses used for periodically pumping charges, a Vpp pumping circuit for pumping Vpp charges and a pump control circuit for controlling the Vpp pumping circuit in accordance with output pulses from the ring oscillator.
However, in case that external voltage or internal voltage comprises two types of voltages, for example, among 3.0V, 2.0V and 1.8V, two identical Vpp pumps need to be provided and then the external voltage and the internal voltage must be controlled with different mask options (metal options). Therefore, a protection circuit against a leak current and an unstable state the so-called latch-up state cannot be realized.